I am using TFT 0.1.4.10 on OS X 10.5.8 in Firefox 5, though it also had the same issue in Firefox 4. When I select text using the Wiki Code, the following code is generated every time, regardless of the chosen color in the menu:

<span style="color:#000000">References</span>

Other than that, this extension has been invaluable. Keep up the great work!